The objectives of the proposed research are to delineate the erythrocyte membrane peptides involves in several interrelated ATP dependent membrane functions, namely, calcium transport, sodium transport and the maintenance of membrane shape and deformability, and to define the mechanism by which they subserve these functions. The structure and function of these membrane constituents will also be evaluated in the erythrocytes from patients with the genetically determined hemolytic anemia, hereditary spherocytosis. Sodium and calcium transport and their interrelationships will be examined using resealed erythrocyte ghosts and sealed inside-out and right-side-out vesicles. Cation flux, cation stimulated ATPase activity and cation regulated phosphopeptide formation will be assessed simultaneously or concurrently. The effects on these functions of cations, nucleotides and inhibitors applied independently to the intracellular and extracellular faces of the membrane will be explored. The maintenance of membrane deformability, an ATP dependent, cation regulated membrane function, appears to be subserved by an actomyosin-like membrane protein fraction. Preliminary studies indicate that this fraction is phosphorylated by ATP but the product differs substantially from the phosphopeptides involved in cation transport. The structural and enzymatic properties of these membrane proteins will be evaluated in situ as well as in their isolated state. Erythrocytes from patients with hereditary spherocytosis are rigid and leaky to sodium. The nature of the defect appears to reside in the regulation of the functions described above, and is thus appropriate to study by the methods outlined.